Developing a Strategy for Sustainable Improved Soil Productivity in the Tropics - Efficient Management of Crop Residue/Farm Waste

Summary

Harvest index, which measures the economic harvest of a crop, often refers to that part of a crop representing that which can be eaten or sold to others for consumption; in smallholder farming. The remainder of the crop, referred to as crop residue; is either fed to livestock, used to build fences, used as mulch, ploughed in (where such equipments are available) or burnt in small-scale farming, causing environmental pollution. These crop residues are also rich in nutrients that were extracted from the soil, used in the building of the edible parts and contribute to soil mining if not returned to the soil. This is a major bottleneck among smallholders as harvesting could take place when the soil is too dry to turn easily or they may not have the labour to do so. If they are to continue to improve productivity, returning nutrients from crop residues back to the soil is a practice farmers must undertake to maintain the soil’s fertility without resort to chemicals that can have negative impacts on the soil and the environment. Many smallholder farmers do not own livestock that can be used to process residues, and so they resort to burning of the residues so that the ash will be available to apply as a form of fertilizer. Burning residues result in the loss of most nutrients through volatilization; and the pollution of the environment through production of green house gases, contributing to global warming. If fed to livestock in-situ, they may not reap the full benefit of the crop residue as animals will leave the field after feeding and thus the excrement produced subsequently is not available as manure. To overcome this bottleneck, a method of composting is advocated where crop residues can be chopped in smaller bits, mixed with contents from the rumen of ruminants obtained from abattoir and some water and ensilaged in a pit or containers for some days to decompose. The same process can also be used for non-consumable parts of products taken to the market or home, so that the decomposed product (compost) is then returned to the farm to improve the soil’s fertility. Application of compost will build up the soil’s organic N, the loss of which is implicated in the loss of the soil’s productivity.